Extreme wide angle lens system

ABSTRACT

A wide-angle lens system having twelve elements, a focal length of 1.0, a focal aperture of 1:2.8, and a field angle of 180*, and wherein the radii of curvature of the refracting surfaces, the axial separations between consecutive refracting surfaces, the refractive indices of the individual lens elements, and the Abbe numbers for each of the lens elements are specified to correct lateral chromatic aberration.

[72] Inventor Toshlnobu Ugura Sakai-sill, Japan [2 l 1 Appl. No. 810.094 [22 Filed Mar. 25. 1969 [45] Patented Aug. 3, 1971 [73] Assignee Minalta Camera Kabushiki Kalsha lsaka, Japan (54] EXTREME WIDE ANGLE LENS SYSTEM 3 Claims, 5 Drawing Figs.

[52] U.S. Cl 350/198. 350/205, 350/2 l4 [Sl Int. Cl ..G02bl3/00, G02b 9/00 [50] Field olSearch 350/198, 205, 2 l 4 Primary Examiner-David Schonberg Assistant Examiner- Paul A. Sacher Auorney- Watson, Cole, Grindle and Watson ABSTRACT: A wide-angle lens system having twelve elements, a focal length of L0, a focal aperture of 1:2.8, and a field angle of l80, and wherein the radii of curvature of the refracting surfaces, the axial separations between consecutive refracting surfaces, the refractive indices of the individual lens elements, and the Abbe numbers for each of the lens elements are specified to correct lateral chromatic aberration.

YIO H2 H5 H8 r20 Y9 l'll H3 & cs d9 as G7 G91 G11 0.0l O 0.0l -0.0l O 0.01 -IOO O IOO% INVENTOR fosu nlolbu 07a R 0 BY wa caafiM-wan ATTORNEYS EXTREME WIDE ANG LE LENS SYSTEM BACKGROUND OF THE INVENTION There are some extreme wide-angle lens system with an angle coverage of up to l80-. However. such prior lens system are not useful in practice because the lens structures have low light intensity owing to a comparatively small relative aperture which results from various problems such as difficulty in correcting the lateral chromatic aberration. the strong residual monochromatic aberrations, and the limited dimension of lens elements and so forth.

SUMMARY OF THE INVENTION The primary object of the present invention is to provide an extreme wide-angle lens system with a relative aperture of up to F/2.8 by eliminating the said defects of prior lens systems and correcting the lateral chromatic aberration, which has been most difficult to remove, to the same degree as that of usual lens systems. Another object of the present invention is to provide an extreme wide-angle lens system which is applicable to a 35 mm. single lens reflex camera with no fear of contact with a reflecting mirror by making the back focal distance over twice the focal length. A further object of the present invention is to provide an extreme wide angle lens system having sufficient light intensity up to the border region corresponding to the half field angle of 90 with excellent image-forming ability so that this lens system is applicable for photographing a whole semispherical field of view when important objects prevail to the border region and is useful when the whole field of view is desired to form round image on film.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I shows the structure of the first embodiment of the present invention of an extreme wide-angle lens system, FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 1 and FIG. 2 an extreme wide-angle lens system of the present invention comprises twelve lens elements, including an interchangeable filter G 7, which are disposed in eight to 10 lens components. Both the first lens element G l and the second lens element G 2 are divergent meniscus lenses which are disposed with the convex surfaces facing to the object side, the third lens element G 3 is a divergent lens, the fourthlens element G 4 is a biconvex lens, the fifth lens element G 5 is a divergent meniscus lens which is disposed with the convex surface facing the object side, the sixth lens element 0 6 is a convergent lens, the seventh lens element G 7 is a filter, the eighth lens element G 8 and the ninth lens element G 9 composing a cemented doublet are a convergent meniscus lens and a divergent meniscus lens, respectively, which are disposed with the convex surface facing the image side. the tenth lens element G 10 and the eleventh lens element G 11 composing a cemented convergent doublet are a divergent lens and a biconvex lens, respectively, and the twelfth lens element G 12 is a biconvex lens. A couple ofG 3 and G 4 and a couple ofG 5 and G 6 are either or both used as cemented doublets. An extreme wide-angle system of the present invention satisfies the following description conditrons.

where r r the radii of curvature of the refracting surfaces numbered in sequence from the object side,

d,, d,... the axial separations between consecutive refracting surfaces,

N,, N the refractive 'indices oflens elements,

V V the Abbe numbers of lens elements,

f the focal length of the whole system.

A filter G 7 can be removed from the system when unnecessary or can be positioned behind the last lens element G 12. Usually, a stop is positioned between G 6 and G 7.

Features and functions of the structure of the lens system of the present invention will be described in the following.

The first three lens elements from the object side are divergent lenses in order to let light penciles introduced at half field angle of incline with not excessive angle in the lens system and to obtain a long back focal distance. The considerable lateral chromatic aberration produced therein must be reduced as much as possible and compensated with the aberration of the opposite sign to be produced by the subsequent convergent lens elements.

The condition (a) gives the range to be satisfied for this purpose. When the condition is not fulfilled, satisfactory cor rection cannot be attained with any selection of Abbe numbers of the lens elements in the rearward portion. The condition (b) is necessary for the three convergent lens elements in the rearward portion from the stop in order to correct the longitudinal chromatic aberration produced excessively by the selection of Abbe numbers in the front portion from the stop as mentioned in the condition (a) and to attain a further correction for the residual lateral chromatic aberrations.

It is necessary to obtain an appropriate value of the Petzval sum, since the lens system covers a half field angle as wide as of 90. The condition (c) is an effective measure to compensate the negative tendency of the Petzval sum caused by the existence of the intensive divergent lens elements in the front portion of the lens system and to eliminate the spherical aberration produced by the convergent lens elements. However, in order to obtain a large aperture of up to F/2.8 for an extreme wide angle lens system, it is necessary to eliminate the higher order aberrations overcorrected by the condition (c) and to correct the coma. For this purpose the condition (11) must be satisfy regarding the refractive indices of air lenses or cemented surfaces formed by G 3 and G 4 and by G 5 and G 6. In order to reduce the magnitude of the spherical aberration and the astigmatism as much as possible while keeping a long back focal distance, it is necessary to dispose three lens elements in the rearward portion from the stop and the condition (e) is required for curvatures ofthe said elements. I

Three embodiment of the present invention based on the above mentioned conditions are described in the following. G 7 is an interchangeable filter as mentioned already, and in cases the filter is removed or positioned at the last portion of the system. In the third embodiment, d ==d =0 means cemented doublets.

- EMBODIMENT I 1:2.8,

[t= 1, Field angle 2w.=180, Back focal distance =2.26]

Radli of Axial Refractive Abbe curvature separations indices Number d =0.12 Ni=l.6700 V =57.2 I't=1.3140

EMBODIMENT I -Continued EMBODIMENT III-Continued Field w Back focal l [i=1 1 2.8. Field angle In 180. Back focal dislance=2.26l

Radii of Axial Refractive Abbe Radii of Axial Refractive Abb curvature separations mdices Number curvature separations indices Numbers rT mm d =0.075 r =4.4599 m=l.5ml d1=0.6303 N4=1.T440 V4==44.9

du=0.7739 N:=l.7545 Ve=32.8 rg=-3.3964 r|1=28.885 j d =0 009 diz=0J rn=2.4672 I TH= V d9=0.l Ns=1.6700 V5=57.1

du=0.0915 N7=L5994 \'7=40-8 I'w=1.1609 I H di0= du=0.3058 l'u=l.1609 1 5:44.966 1 d"=0.35s1 Ni=i.7545 v.=32.s

dls=0.4331 I N =L6388 .=eo.1 m=11.e24 l m=-0-6905 di2=0.1 1 d1.=o.1 x.=1.re1s v==26.5 I5 =m a d|;=0.0915 N1=1.5994 V1=40.s

dn=0.009 r n m 7.5358 a =o.2992 d1 =0.085 Nm=L7400 io=37.5 m=-i.4674 m=L4093 d=0.3929 Ns=1.6388 V =60.1

di =(l.5l N =1.6230 V|1=58.1 m=-0.6287 2 7 l d q=0.1 No=1.7557 Vl=27.2

dm=o.oo9 l n,-=-1.a94a m=3.0419 d1 =0.009

dn=O.265 I NI1=L5IGS V g=64.2 r g=28.137 m=-I6.393 d1a=0.085 Nm=L7400 V o=37.5

2d=4.4265 l m=1.6430

l d1o=0.47 N11=1,6688 V i=56,0

I20=2.U126 dzu=0.009 EMBODIMENT II =4 0703 d =0.305 N =1.5188 V =64.2 =1, 122.8, Field angle 2u=180, Back iocal distance=2.26] =a,9 3o I I 2d=4.4622 Radii of Axial 1 Refractive Abbe curvature separations Indices f numbers E FIG. 1 and FIG. 2 illustrate the structure of the lens system n=9A375 l of the first and the third embodiments, respectively.

di=0.1300 N =1.6010 Vi=64.1 FIG. 3, FIG. 4, and FIG. 5 show the behavior of the cor- 12:05am rected aberrations of the first, the second, and the third emn=3.0619 5 v bodiment, respectively, where each aberration is proved to be :13581 dfimzm F603 well corrected in spite of the aperture of up to F/2.8 at a half 3 7 d4=0.5B96 field angle of 90 while keeping a long back focal distance. f5=

' d$=0l0m N;=1.6204 v,=eo.s n=6.3335 l. A wide angle lens system having a focal length of L0, a n=3.2901 dFomso 40 focal aperture of 1:2.8, a field angle of l80, and 12 elements d1=0.6092 N4=1.7440 Vi=44.9 successively mounted from the object side, comprising; "F (18:00090 first and second lenses of the divergent meniscus type each n=2.3791 having a convex surface facing the object, F1 1269 NEW-mo :571 a third lens of the divergent type,

dm=0.0750 a fourth lens of the biconvex type, i i=L3096 dn=om76 l N.=L7545 :323 a fifth lens of the divergent meniscus type having Its convex m= 430.030 surface facing the ob ect, m: m 112:04000 a sixth lens of the c onvergent type,

du=0.0915 N1=L5994 V1=40.B a seventh element is a filter, l'u=m =o3013 eighth and ninth lens elements formed as a doublet lens, m=1.5805 7 said eighth lens is of the convergent meniscus type. said m= 06509 NFLW i F604 ninth lens is of the divergent meniscus. type. said eighth du=0.1000 N;=1.7557 1 Vn=27.2 and ninth lens each having a convex surface facing the m=1.3394 i g dn=0-0090 n|=-7.3099 l tenth and eleventh lenses formed as a convergent doublet m=1 4905 P315 lens, said tenth lens is a divergent lens and said eleventh I di|=0.4700 Nu=1.5688 V1i=56.0 lens is a biconvex lens, da=0009 a twelfth lens of the biconvex type, and wherein the inm=3.4516 I dicated lens elements have the following characteristics, (h1=0.3050 Nu=l.5168 vu=64.2 r =4.9417 Ed 3634 6O d =0.13 Ni=1.6010 V1=64.1 I':=1.306O EMBODIMENT 1n :2 9757 [i=i, 1:2.8, Field angle 20 18)", Back local distance=2.26] d;=0.12 N2=l-670O Vz=57.1

- r=1.3140 l d4=0.5913 Radii 0i Axial Retractive Abbe r =3.1775 curvature separations indice: Numbers d.;=0.1 Ni=1.6204 V;=60.3

' ri=s2.oe2

3 171 du=0.075 r =9.8377 r1= 8 t d|=0.i3 =1.60l0 Vi=64.1 70. V d =0.5131 N=1.6676 V4=4L9 r=1.3114 ig=5.3920

I d;=0.55r s 2 3056 ds=0.009 r =3.0629 r a d;=0.12 \';=l.6204 V2=60.3 di=0.1 N5=1.6214 V5=6L2 r =3.0629 r =1.1154

3 2069 dl=0.5975 I 15001 d1o=0.075 r r1 5 I d;=0.l N;=1.6Z)-i V3=60.3 l d| =0.2739 Ne=l.7545 Va=32.8 r =4.4 599 l rn=28-885 V wherein r, r,...r are the radii of curvature of the refracting surfaces as indicated in HO. 1,

d d,...d,, are the axial separations between consecutive refracting surfaces,

N,, N,...N,, are the refractive indices of the respective lens elements,

V,, V,,,...V are the Abbe numbers for the respective lens elements, and

the back focal distance of the lens system is 2.26.

2. A wide angle lens system having a focal length of 1.0, a

focal aperture of 1:2.8, a field angle of I80", and 12 elements successively mounted from the object side, comprising;

first and second lenses of the divergent meniscus type each having a convex surface facing the object,

a third lens of the divergent type,

a fourth lens of the biconvex type,

a fifth lens of the divergent meniscus type having its convex surface facing the object,

a sixth lens of the convergent type,

a seventh element is a filter,

eighth and ninth lens elements formed as a doublet lens, said eighth lens is of the convergent meniscus type, said ninth lens is of the divergent meniscus type, said eighth and ninth lens each having a convex surface facing the image,

tenth and eleventh lenses formed as a convergent doublet lens, said tenth lens is a divergent lens and said eleventh lens is a biconvex lens,

a twelfth lens of the biconvex type, and wherein the indicated lens elements have the followingcha acteristics, 4

3. A wide angle lens system having a focal length of 1.0, a

focal aperture of l:2.8, a field angle of I80", and 12 elements successively mounted from the object side, comprising;

first and second lenses of the divergent meniscus type each having a convex surface facing the object,

15 a third lens of the divergent type,

a fourth lens of the biconvex type, a fifth lens of the divergent meniscus type having its convex surface facing the object, a sixth lens of the convergent type, a seventh element is a filter,

eighth and ninth lens elements formed as a doublet lens. said eighth lens is of the convergent meniscus type, said ninth lens is of the divergent meniscus type, said eighth and ninth lens each having a convex surface facing the image,

tenth and eleventh lenses formed as a convergent doublet lens, said tenth lens is a divergent lens and said eleventh lens is a biconvex lens, a twelfth lens of the biconvex type, and wherein the indicated lens elements have the following characteristics,

ri=9.fi'l7 d =0.13 Nt=1.6010 V1=64.1 r,=1.3114

e=0.5558 ra=3-0629 d, =0.12 N,=1.6204 V =60.3 r4=3.0629 40 :32069 dl=ot5 7fi d =0.1 N;=I1.6204 V;=60.3 r.=4.4599

da= r1=4.4599

d =0.6303 N4=1.7440 V4=44.9 lg=3.3964

d =0.009 l'a=2.4672

d'=0.1 N5=L67tll V5=57.1 r =1.16O9

dm=0 tn=1.1609

du=0.3581 NI=L7645 Vu=32.8 o l'n=l7.624

dis=0-0915 N1=l.5994 V1=40.8 u=

d|t=0.2992 rrs=1.4674

d15=0.3929 N5=1.6388 Vg=60.1 r1 =0.6287

d t=0.1 Nu=1.7557 Vo=27.2 rum-1.3943

d1 =0.085 Nro=L7400 Vto=37.6 m=1.6430 0 d1 =0.47 Nu=1.6688 Vu=56.0

raw-2.0126

dzo=0.009 r1t=4.0703

dzt=0.305 Nu=1.5168 Viz-64.2 Izz=3.9130

wherein r, r ...r are the radii of curvature of the refracting surfaces as indicated in FIG. 2, d dg-udz are the axial separations between consecutive refracting surfaces, N,, N ...N, are the refractive indices of the respective lens elements, V V ,,...V are the Abbe numbers for the respective lens elements, and the back focal distance of the lens system is 2.26. 

1. A wide angle lens system having a focal length of 1.0, a focal aperture of 1:2.8, a field angle of 180*, and 12 elements successively mounted from the object side, comprising; first and second lenses of the divergent meniscus type each having a convex surface facing the object, a third lens of the divergent type, a fourth lens of the biconvex type, a fifth lens of the divergent meniscus type having its convex surface facing the object, a sixth lens of the convergent type, a seventh element is a filter, eighth and ninth lens elements formed as a doublet lens, said eighth lens is of the convergent meniscus type, said ninth lens is of the divergent meniscus type, said eighth and ninth lens each having a convex surface facing the image, tenth and eleventh lenses formed as a convergent doublet lens, said tenth lens is a divergent lens and said eleventh lens is a biconvex lens, a twelfth lens of the biconvex type, and wherein the indicated lens elements have the following characteristics,
 2. A wide angle lens system having a focal length of 1.0, a focal aperture of 1:2.8, a field angle of 180*, and 12 elements successively mounted from the object side, comprising; first and second lenses of the divergent meniscus type each having a convex surface facing the object, a third lens of the divergent type, a fourth lens of the biconvex type, a fifth lens of the divergent meniscus type having its convex surface facing the object, a sixth lens of the convergent type, a seventh element is a filter, eighth and ninth lens elements formed as a doublet lens, said eighth lens is of the convergent meniscus type, said ninth lens is of the divergent meniscus type, said eighth and ninth lens each having a convex surface facing the image, tenth and eleventh lenses formed as a convergent doublet lens, said tenth lens is a divergent lens and said eleventh lens is a biconvex lens, a twelfth lens of the biconvex type, and wherein the indicated lens elements have the following characteristics,
 3. A wide angle lens system having a focal length of 1.0, a focal aperture of 1:2.8, a field angle of 180* , and 12 elements successively mounted from the object side, comprising; first and second lenses of the divergent meniscus type each having a convex surface facing the object, a third lens of the divergent type, a fourth lens of the biconvex type, a fifth lens of the divergent meniscus type having its convex surface facing the object, a sixth lens of the convergent type, a seventh element is a filter, eighth and ninth lens elements formed as a doublet lens, said eighth lens Is of the convergent meniscus type, said ninth lens is of the divergent meniscus type, said eighth and ninth lens each having a convex surface facing the image, tenth and eleventh lenses formed as a convergent doublet lens, said tenth lens is a divergent lens and said eleventh lens is a biconvex lens, a twelfth lens of the biconvex type, and wherein the indicated lens elements have the following characteristics, 